Ionizable compounds and compositions and uses thereof

A compound comprising the structure shown in Formula IV

• wherein R1 and R2 are
• R1═C(═O)OR4
• R2═C(═O)OR5
• wherein R4 and R5 are independently for each occurrence a C(12-20) alkyl group, or a C(12-20) alkenyl group:
• wherein R3 is selected from
• wherein
• each R6 is independently selected from H, alkyl, hydroxyl, hydroxyalkyl, alkoxy, alkoxyalkoxy, and aminoalkyl;
• each R7 is independently selected from H, alkyl, hydroxyalkyl, and aminoalkyl;
• each R8 is independently selected from H, alkyl, hydroxyalkyl, and aminoalkyl, and any two R8 may form a ring;
• q is from zero to four;
• Q is O or NR7;
• p is from 1 to 4.